Load-control backup signal generation circuit
View Patent ↗In a case in which a malfunction occurs in a control processor which operates according to a predetermined program, a load-control backup signal generation circuit supplies a backup control signal to a switch of a load connected to an output of the control processor. The load-control backup signal generation circuit includes: a watchdog input terminal to which a watchdog signal periodically output from the control processor is input; a pulse count unit which counts a clock pulse generated with a constant period and which controls a count state of the clock pulse according to a signal input to the watchdog input terminal; and a backup signal output unit which generates the backup control signal when a count output of the pulse count unit satisfies a predetermined condition.
1. A load-control backup signal generation circuit which, in a case in which a malfunction occurs in a control processor which operates according to a predetermined program, supplies a backup control signal to a switch of a load connected to an output of the control processor, said load-control backup signal generation circuit comprising:
a watchdog input terminal to which a watchdog signal periodically output from the control processor is input;
a pulse count unit which counts a clock pulse generated with a constant period and which controls a count state of the clock pulse according to a signal input to the watchdog input terminal; and
a latch circuit comprising a D input terminal connected to a power supply line and a latch input connected to an output of the pulse count unit to receive an output signal of the pulse count unit, the latch circuit outputting the backup control signal based on the power supply line in response to the output signal latching the latch circuit.
2. The load-control backup signal generation circuit according to claim 1 , further comprising:
a DC-cut capacitor connected between the watchdog input terminal and a control input terminal of the pulse count unit; and
a potential-control resistor connected between the control input terminal of the pulse count unit and a power supply line having a predetermined potential.
3. The load-control backup signal generation circuit according to claim 1 , further comprising:
a clock pulse generator which generates the clock pulse with the constant period.
4. The load-control backup signal generation circuit according to claim 1 ,
wherein the pulse count unit retains a state of the generated backup control signal in the latch circuit, when the output signal of the pulse count unit latches the latch circuit.
5. A load-control backup signal generation circuit which, in a case in which a malfunction occurs in a control processor which operates according to a predetermined program, supplies a backup control signal to a switch of a load connected to an output of the control processor, said load-control backup signal generation circuit comprising:
a watchdog input terminal to which a watchdog signal periodically output from the control processor is input; and
a processor configured to:
count a clock pulse generated with a constant period and which controls a count state of the clock pulse according to a signal input to the watchdog input terminal; and
receive a count output at a clock input of a latch circuit and output a backup control signal based on a power supply at a D input of the latch circuit in response to the count output satisfying a predetermined condition.